GPT-5.5's Daily Trail Archive feature creates persistent puzzle history for Signal Garden — a player can revisit past daily challenges, see their completion patterns, and track progress over time. This transforms Signal Garden from a daily-use tool (play today's puzzle) to a persistent engagement platform (build a streak, revisit favorites, compare patterns). The archive also functions as a content moat: even if new puzzles slow, the existing archive provides continued value. Combined with mobile UX improvements and direct-to-board Hub links, the Trail Archive is the infrastructure for sustained player relationships rather than one-off daily visits.